CF4 Capture and Separation of CF4-SF6 and CF4-N2 Fluid Mixtures Using Selected Carbon Nanoporous Materials and Metal-Organic Frameworks: A Computational Study.

Ioannis Skarmoutsos,Emmanuel N Koukaras,Emmanuel Klontzas

doi:10.1021/acsomega.1c06167

Abstract

The adsorption of pure fluid carbon tetrafluoride and the separation of CF4–SF6 and CF4–N2 fluid mixtures using representative nanoporous materials have been investigated by employing Monte Carlo and molecular dynamics simulation techniques. The selected materials under study were the three-dimensional carbon nanotube networks, pillared graphene using carbon nanotube pillars, and the SIFSIX-2-Cu metal–organic framework. The selection of these materials was based on their previously reported efficiency to separate fluid SF6–N2 mixtures. The pressure dependence of the thermodynamic and kinetic separation selectivity for the CF4–SF6 and CF4–N2 fluid mixtures has therefore been investigated, to provide deeper insights into the molecular scale phenomena taking place in the investigated nanoporous materials. The results obtained have revealed that under near-ambient pressure conditions, the carbon-based nanoporous materials exhibit a higher gravimetric fluid uptake and thermodynamic separation selectivity. The SIFSIX-2-Cu material exhibits a slightly higher kinetic selectivity at ambient and high pressures.

Highlights

One of the main aims of international environmental treaties and agreements, such as the Kyoto Protocol and the ParisAgreement within the United Nations Framework Convention on Climate Change, is to reduce greenhouse gas emissions in the atmosphere in order to prevent dangerous anthropogenic interference with the climate system.[1,2] For this reason, six categories of greenhouse gases, sometimes distinguished as CO23 and non-CO2 ones,[4] have been classified among the most potent ones
As mentioned in the introduction, two types of carbon-based nanoporous materials were investigated in the framework of the present study
The first type is a porous nanotube network (PNN),[37] composed of (8,8) single-walled carbon nanotubes which are connected through junctions, forming a threedimensional cubic carbon nanotube network with an intertube distance of 11 Å and a corresponding three-dimensional porous network

Summary

Introduction

Agreement within the United Nations Framework Convention on Climate Change, is to reduce greenhouse gas emissions in the atmosphere in order to prevent dangerous anthropogenic interference with the climate system.[1,2] For this reason, six categories of greenhouse gases, sometimes distinguished as CO23 and non-CO2 ones,[4] have been classified among the most potent ones. These greenhouse gases are carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), hydrofluorocarbons, perfluorocarbons (PFCs), and sulfur hexafluoride (SF6). The recycle of CF4 from CF4/N2 mixtures is important in a wide range of applications involving a positron trap[9] since these mixtures are used as buffer gases for the cooling of positrons.[10]

Objectives

Methods

Results